Variable electric resistance



April 22 1924. 1,491,170

K. ROT-TGARDT VARIABLE ELECTRIC RES IST ANCE Filed Dec. 5. 1921 INVENTOR BY fi W ATTORNEY Patented Apr. 22

T0all'whonu'tmayconcern:

UNITED STATES PATENT OFFICE.

Application fled December 5, 1831. Serial Ho. 519,928.

' able resistance material and a plunger adapt- Be it known that I KARL Rorrmann'r, en,- 'neer, residing at l)ahlem, near Berlin,

naling impulses, such as voice currents, and rman have invented certam new and to thereby vary the-pressure between the resistance ed to oscillate infresponse to electrical sig- I f, then, a microphone re the same I useful mprovements'in Variable Electric Resistance, of which the following is a specification.

The invention relates to variable electric resistance devices, and is directed, more particularly, to improvements in microphonic re aters. v

e object of the invention is the provision of a microphonic repeater or am lifier which will function without distortion, or at least with less distortion than results from similar devices heretofore known.

It is well known that acoustic diap of all types have-natural "ods and u they respond to and rep When, for example, sound waves are pressed upon atransmitter ha anacous-'- tic diaphragm and then rep uced ha! a receiver likewise having an acoustic 'a-. hragm, some of the notes, are. distorted th at the transmitter and at the receiver,

due to the fact that the diaphragms of both the transmitter and-receiver do not rend in proper proportion to these notes.

a diaphragm' is m mission line between mg receiving stations, it isevident that still further distortion is likely to result from phragm. Thus it will beseen stantially or entirely eliminated at these re ting stations. I

its referred embodiment the invention contemplates the provision of a microphonic pester comprising a receptacle containuce sound waves 'of different frequencies with difierent del,

' forms. the same function as mheren' tdefectinthere dia- 1 sev' Y eralsuch re ters'were in in the line, thedi tz rtion might be carried to such an extent that the signals would be sists of a 'constantly rotating attheintermediatere tth carbon granules or equivalent veri-' carbon granules, thus efiect' variations corresponding with t e electrical signalin waves. In other words, the repeater e ement of invention is a carbon microphonein which a plunger is substituted for the usual diaphragm-thzglunger 'as m having no natural 0 ating peri the case of the dia fi this -kind is incap sound waves with sufiicient ener agm. -A device of to render it useful 85m transmitter, but in combina-- tion with a rela of the described in British Patent 0. 144,7 61, 1t is capable of operating efiiciently as a repeater.

In the accompanying drawing 1e of responding to} i Fig. 1 is a diagrammatic illustration of one embodiment of-the invention; and

1 Fig. 2 is a diagrammaticillustration of-vfln' alternative embodiment.-

b; is a receptacle, preferahlyof non-conduct' material, into which the of con uctors V and Z extend. The space W within the receptacle 6 is filled with car-,

bon granules or equivalent material, and a ginger S is arranged ly oscillated to efiect ch of pres sure between the carbon gran es and thus efimt orresponding resistance variations he- -so that it may b tween the terminals of the conductors V and Z. It will be seen that the 1 r8 per- 516 ifiaphragm of an ordinary microphone, but thispl has no eflectlve natural period. The

which is arranged to operate theplunger' m response to electrical voice signals an the like which it is desired to repeat, conas is clearly described'in the aforemention disccwhielz British patent, may consist of any one of 7 several materials which are characterised by their Zoor conductivity, such as slate or agate. metal band a bears against the C and vtlm other to the band a. The

periphery of the disc C and is'restrained by band. a isvariably attracted to the Cinresponsetothe inco current, andacco lythe tweenthediscCa'nd ahng it; be-

mand a is varied. In response to this-variable frietionthe plungof the present invention, it is thought to be unnecessary to describe it-in any detail herein.

The modified embodiment of the invention shown in Fig. 2 difiers from that of Fi 1 only in that the plunger S is provifed with a head E having a considerable area.

In the appended claims the term carbon granules should be construed as including all equivalent materials whether they are in the form of granules or otherwise, as,

V for instance, a plurality of superimposed carbon discs.

I claim: 7 1. A microphonic repeater comprising a variable resistance element, and a plunger adapted to be oscillated in accordance with signals to be repeated.

2. A microphonic repeater comprising a receptacle, carbon granules contained in said receptacle, an oscillatory plunger insertedin said receptacle adapted u on being oscillated to vary the pressure tween said anules.

3. n combination, a microphonic repeater comprising a variable resistance element and an oscillatory plunger adapted to vary the resistance through said resistance element in accordance with signal currents to be transmitted, and a relay for operating said plunger in accordance with said si nals, said relay comprising a continuous y rotating member and a relatively stationary member in frictional engagement therewith, said stationary member being connected with said plunger for transmitting oscillatory movements thereof, the arrangement being such that the frictional engagement between said rotating member and said relativel stationary member varies in accordance with the transmitted signals.

In tBStimOIII; whereof I afiix my 51 ature.

' a. KARL ROTTG DT. 

